The present invention relates to a device for assisting focusing of a camera, equipped with a manual focusing apparatus, for providing digital image contents, more particularly a smart camera, a camera equipped with such a device and a method for providing focusing information.
“Smart cameras” are understood to mean optical systems which are able not only to record images but also to process and/or interpret these independently. By way of example, in addition to an image recording circuit, a smart camera can, as intelligent and autonomous optical system, also filter out and process application-specific information from recorded images and make decisions based thereon.
Smart cameras, which are often utilized within the scope of monitoring objects, generally consist of a camera housing with a video processing unit (video content analysis) and a removable lens. Depending on the application, use can be made of different lenses (wide-angle, telephoto or zoom lenses). After a new lens has been mounted, the latter generally needs to be focused manually. In the case of a smart camera, the latter is, for this purpose, usually connected to a computer (e.g. a notebook) via a network connection, for example via Ethernet or WLAN. The camera image can subsequently be observed on the notebook while the lens is set to have the best focus.
A focusing apparatus, which can be used in such smart cameras, or a recording lens with a changeable focal length is disclosed in e.g. DE 23 61 286 A1. Automatic methods for motorized focusing of a lens (i.e. autofocus methods) are known from DE 692 07 043 T2 and EP 0 508 897 B1, for example. However, in the case of monitoring objects, in which use is made of fixedly installed, static cameras, more cost-effective lenses without autofocus functionality are preferred. Here, manual lenses are therefore particularly advantageous as a result of the fact that the lens is generally only set once during the installation of a camera, and subsequently remains unchanged in terms of the focus position.
When focusing a smart-camera system in which an external display of the camera image, for example on a notebook, is used in order to set a precisely sharp focus, it is necessary to observe the screen continuously in order to obtain the best sharpness result. However, in situations in which the camera is mounted at large distances, for example at great heights on ceilings or other points that are difficult to access, it is hardly possible to appraise the camera image and simultaneously adjust the lens. Such situations often present no option for placing down a computer, e.g. a notebook, within viewing distance of the camera.
There therefore is a need for apparatuses for assisting focusing of corresponding cameras, in particular smart cameras, which apparatuses can be used on cameras which merely have a manual focusing apparatus.